Video systems are commonly used throughout the commercial, industrial and military establishments for surveillance of areas for security reasons and general observation of activities and events. These systems usally utilize a black and white or color TV camera with a fixed focal length or zoom lens, and a TV monitor located remotely from the camera. With this type of system the camera is restricted to view in one direction, however the size of the area or field of view (FOV) may be controlled with a zoom lens. Some of the more complex systems provide for remote control of the zoom lens, thereby providing remote control of FOV. Whatever the case, the camera is viewing in only one direction and the center of the field of view does not change.
For surveillance situations that require the camera's FOV to be moved horizontally or vertically, a pan and tilt mechanism is used. This is a two-axis motorized device that can tilt the camera vertically up and down and pan the camera horizontally back and forth. These devices can be remotely controlled and can be programmed to move in some prescribed scenario or can be manually controlled by an operator who has a controller connected to the device.
The pan and tilt mechanism offers the advantage of providing wide angular excursions of camera tilting and panning. However, there are several disadvantages in their use. Some of these are:
a. They are heavy and cumbersome since they use electric motor drives. PA1 b. They are large in size compared to the TV camera and require considerable space for their housing. PA1 c. They are limited in speed at which they can pan and tilt the camera. PA1 d. The movement of the camera can be seen by those being observed. This may be undesirable in locations such as banks, gaming facilities and areas where personnel performance is being measured. PA1 e. They are expensive to obtain.